From a6ce75fa2d560ebe7e8fd9895cadc611d42fb290 Mon Sep 17 00:00:00 2001
From: Riccardo Casatta <riccardo@casatta.it>
Date: Mon, 12 Jul 2021 10:06:08 +0200
Subject: [PATCH] [docs] clarify when the fee could be unknown

---
 src/types.rs | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/types.rs b/src/types.rs
index ab635ee1..ddd498aa 100644
--- a/src/types.rs
+++ b/src/types.rs
@@ -160,7 +160,10 @@ pub struct TransactionDetails {
     pub received: u64,
     /// Sent value (sats)
     pub sent: u64,
-    /// Fee value (sats) if available
+    /// Fee value (sats) if available.
+    /// The availability of the fee depends on the backend. It's never `None` with an Electrum
+    /// Server backend, but it could be `None` with a Bitcoin RPC node without txindex that receive
+    /// funds while offline.
     pub fee: Option<u64>,
     /// If the transaction is confirmed, contains height and timestamp of the block containing the
     /// transaction, unconfirmed transaction contains `None`.